After the unsuccessful attacks against the Persian front, No'man bin Muqarrin called a council of war to decide the future course of action for the Muslim army.
After discussion, it was decided that the following stratagem should be adopted:
1. A rumour should be spread that Umar the Caliph was dead.
2. The Muslim army should start moving back giving the impression that it was withdrawing because of the death of the Caliph and resistance of the Persians.
3. When the Persians advance to pursue the Muslims, the Muslim army should turn round and fight.
4. In the meantime Qaqaa with the cavalry should outflank the Persian army and try to reach the rear thus cutting the retreat of the Persians.
For a week there was no Muslim attack. Then the Persians heard reports of the death of the Caliph. The news spread like wild fire, and the Persians felt jubilant. As Mardanshah heard of the news he felt convinced that he would be in a position to take revenge from the Muslims for the previous Persian defeats.
And then the Persian scouts carried the news to Mardanshah that the Muslim army had struck their camps and were withdrawing. Mardanshah gave the call to arms, and dashed forward with his army in pursuit of the withdrawing Muslims.
When Noman came to know of the Persian advance, he quickly ordered the Muslim army into battle formation. Obscured from the Persian view Qaqaa with his cavalry proceeded to outflank the Persian army.
Addressing the soldiers, Noman exhorted them to fight in the way of Allah. He prayed for the victory of the Muslims and for his own martrydom. He willed that if he was to be martyred, Hudheifa bin Al Yaman was to take over the chief command.
As soon as the Persian army came in sight, the Muslim soldiers became uneasy for an attack. Noman, however, asked them to wait. Mugheera who commanded a wing came to Noman and said, "If I were in chief command I would have ordered action". Noman said that in keeping with the practice of the Holy Prophet he would order the attack after the midday prayers when the winds had begun to blow.
After the midday prayers, Noman give the battle cry, and the Muslim army rushed headlong at the enemy. Under the fury of the Muslim attack the Persian army reeled back. It was a grim and bloody contest and the battlefield was soaked with blood. When the battle was at its climax, in an attempt to advance, the horse of No'man slipped in the blood soaked soil, and fell along with its rider in a pool of blood. Immediately Noman was struck by an arrow shot from the Persian camp. Noman though still alive became unconscious, and with the arrow embedded deep in his side, there was no hope of his survival. Naeem the brother of Noman held the army standard in the place of Noman, and the battle went on without the Muslim army knowing that their Commander had fallen.
Slowly and steadily the Muslim army advanced beating back the Persians. The Persians fought with the courage of desperation. Shortly before sunset, the Persian resistance began to weaken, and the Muslims struck against them with greater violence. The cavalry under Qa'qaa struck against the flanks of the Persian army. Night fell but the Muslims continued the pursuit. In the process of withdrawal the belt of caltrops played havoc with the Persians. An arrow from the Muslim side struck Mardanshah, and covered with blood he fell in the belt of caltrops to die.
In the meantime the news of the death of No'man wag reported to Hudheifa. He took over the command, and in spite of gathering darkness the Muslims pressed on their relentless pursuit of the Persians. The pursuit was carried until the Persians reached a ravine, and here in a frantic effort to escape the pursuing Muslims, the Persians fell down the precipice in thousands.
Out of the 60,000 Persians who had fought at Nihawand, 40,000 were killed. The rest escaped to Hamadan.
The battle of Nihawand was over. The Muslims had once again won an historic victory.
It was midnight when the Muslim army gathered in their camp. The Muslim soldiers gathered around the body of No'man. He still breathed. They washed his face. He stirred and opened his eyes. He asked, "What is the result of the battle".
They said, "Rejoice for God has given us victory".
No'man said, "Praise be to Allah," and with these words he breathed his last.